Hey,

Is this possible to run it in window mode? Maybe some external tools to do it?

I recently got Disciples 1 working in windowed mode with 2x upscaling using DxWnd: https://sourceforge.net/projects/dxwnd/

Here is my DxWnd config file. Unzip the .dxw file and then import it into DxWnd using "File->Import...". You'll probably have to adjust the executable path. You might also need to clear your compatibility flags with "Tools->Clear Compatibility flags". Also, DxWnd options are rather unintuitive, so you'll have to spend time reading the in-app help file: just go to "Help->View help".

DxWnd config file: Disciples 1 (Windowed + 2x HQ UpScale).dxw.7z

DxWnd config file (faster bilinear interpolation):
Disciples 1 (Windowed + 2x Faster).dxw.7z

Try right-clicking on DxWnd.exe and select "Run as Administrator". Then select the "Disciples" icon from inside DxWnd, then select Tools->"Clear Compatibility flags" from the DxWnd menubar.

It worked! Thank you good sir. Ancients bless you

I know this post is over a year old, but is there any way to do this without downloading an external tool?

Open Disciple.ini file and set InWindow=1. But this requires DirectDraw option checked.

Otherwise use third party tools like DxWnd or GL Wrapper

Last one is best solution, which also allows select much more higher resolution for map view.
https://verokster.blogspot.com/2019/03/disciples-i-ii-gl-wrapper-patch.html

check this example https://i.ibb.co/G9Y4VxR/SL-GAME.png